The invention relates to a method of determining oil top-up quantities for an engine.
German Patent document DE 44 29 234 A1 discloses a method of determining the oil consumption of an engine in a vehicle by using a measuring and switching device arranged in the oil sump of the engine. The measuring and switching device determines specific state values of the oil and whether the oil has fallen below a preset level. In this case, the particular state values, the most important engine operating variables and the geometry of the oil sump are taken into account, in order to determine the oil consumption per unit of distance with reference to a distance covered.
Problems which arise in this case are that, as a rule, these measurements work only in an unreliable manner on account of the high dynamics of the oil level. As a result, these measurements may lead to incorrect results due to particular vehicle states, such as, for example, an unlevel position of the vehicle and high acceleration values.
The object of this invention is to overcome the above-described disadvantages of the prior art by providing a possibility of recognition, in order to detect an intermediate oil top-up quantity and to determine its size.
The object is achieved by a method for recognizing oil top-up quantities. The method records a multiplicity of oil levels under specific operating conditions over time; calculates an oil-mass average value X.sub.z of the oil top-up quantity over z instantaneous measurements xmom in each case; calculates a compensating function describing the variation in an oil mass xh over time by means of a specific number of hourly oil masses xh; calculates a difference DFA from an end point xlang of the compensating function describing the variation in an oil mass xh over time and from the penultimate oil-mass average value according to the function (DFA=xlang-X.sub.zN-1) with X.sub.zN-1 being the oil mass penultimately obtained by rolling or weighing averaging from z instantaneous oil masses xmom; activates a discrimination function for checking whether the difference DFA is greater than a first oil-mass limit value M1; and if so, a special case is recognized and a processing function for calculating the oil top-up quantity in the special case is started; and if not, a further discrimination function is started, for checking whether the difference DFA is greater than a second oil-mass limit value M2 and there is a specific communication signal between the vehicle and driver. If the result of the check is that the difference DFA is greater than the second oil-mass limit value M2 and there is a specific communication signal between the vehicle and driver, the method recognizes a special case and the processing function for calculating the oil top-up quantity in the special case is started, if the interrogation result is negative, a processing function for calculating the oil top-up quantity in the normal case is activated.
The present invention accordingly recognizes the following:
Oil top-ups change the oil level in the oil sump. For the reliable calculation of oil consumption, therefore, each top-up of oil must be recognized. The objective for improving oil consumption measurements is consequently the recognition of top-ups in commercially available containers. It must be possible to detect oil quantities of an order of magnitude from 0.5 l with an accuracy of below.+-.0.25 l.
Moreover, the recognition of oil top-up quantities can be used in methods of solution which draw conclusions as to quality or as to a lengthening of the oil-change interval from the determination of the oil top-up quantity and, if appropriate, the topping-up time.
By means of this method and the associated recognition of special cases, it is advantageously possible to go further and differentiate engine damage in terms of the degree of damage.
By setting limits or limit values and evaluating the changing difference between the current X.sub.z values, which correspond to the slope of a straight line, it is possible, for example in the case of serious engine damage, to recommend the driver to visit a workshop immediately, in order to protect the engine from even worse damage or destruction, for example due to piston seizure.
At the same time, "creeping" engine damage can thereby also be recognized during a routine inspection an d preventive measures thus be taken at the workshop.
The measuring method according to the invention is based on the consideration that any individual measurement, for example measurement in the state immediately when starting the engine or when the vehicle is not level or if there is a long oil return time between engine on and engine off, etc., is subject to error. other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.